The check valve shown in the above U.S. patent consists of two members which are assembled to form a valve chamber which encloses a resilient disk and form a valve seat for the disk. One of the chamber forming members includes an inlet tube portion and the other chamber forming portion includes an outlet tube portion.
In the past, these two chamber forming members were assembled by means of sonic welding, spin welding, solvent welding, and the like and the resulting valves had the following disadvantages:
1. Some of the valves were faulty because of dimensional instability in the assembly process caused by the fact that the welding process consumes some of the plastic from which the chamber forming parts of the valve are formed. The result is non-uniformity of the valves during mass production procedures. PA1 2. It was necessary to form both chamber forming parts of the valve of the same plastic material since assembly of the parts required welding of the parts together. PA1 3. The sealing of the valve chamber was totally dependent on the integrity of the welding procedure.